xen/arm: domain_build: Don't continue if unable to allocate all dom0 banks

xen/arm: domain_build: Don't continue if unable to allocate all dom0 banks

Xen will only print a warning if there are memory unallocated when using
1:1 mapping (only used by dom0). This also includes the case where no
memory has been allocated.

It will bring to all sort of issues that can be hard to diagnostic for
users (the warning can be difficult to spot or disregard).

If the users request 1GB of memory, then most likely they want the exact
amount and not 512MB. So panic if all the memory has not been allocated.

After this change, the behavior is the same as for non-1:1 memory
allocation (used by domU).

At the same time, reflow the message to have the format on a single
line.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>